Heart disease remains the leading cause of death in developed countries. About 70 million Americans (more than one-fourth of the population) live with cardiovascular disease, with a death toll that is almost twice as high as that for all cancer combined, and the cost of ~300 billion dollars spent every year to treat the cardiovascular disease (www.americanheart.org/presenter.jhtml?identifier=4478). Tissue engineering offers a potential to grow in vitro functional equivalents of native myocardium for use in tissue repair, and to investigate new ways to treat or prevent the disease. However, major challenges remain, including the need to establish a clinically relevant source of human cells, and to vascularize the engineered tissue, both during the in vitro cultivation and following implantation in vivo. We propose to engineer a patch of myocardial tissue with high capacity for vascularization, by controlling the levels of VEGF presented to the cells. The fundamental question we address is if co-culture of cardiac myocytes and cells expressing controllable levels of VEGF can be utilized to mediate the formation and maturation of a vascular network, during in vitro culture and following implantation onto infarcted myocardium. The immediate goal of this application is to generate synchronously contracting myocardial tissues with ability for vascularization, by bioreactor co-culture of cardiomyocytes and VEGF transfected cells on elastomer scaffolds. We propose a set of focused and well coordinated in vitro studies (bioreactor co-culture of cardiac and VEGF expressing cells) and in vivo studies (in a rat heart infarction model), with the following specific aims: (1) To engineer a cardiac patch based on neonatal rat cardimyocytes and VEGF-transfected myoblasts. (2) To generate adult human stem cells with controllable release profiles of VEGF. (3) To engineer a cardiac patch based on neonatal rat cardiomyocytes and VEGF-transfected human stem cells. In all cases, cells will be cultured on a highly porous, channeled elastomer scaffold, using an advanced bioreactor for cardiac tissue engineering. The viability, functional properties, integration with the host tissue and blood perfusion will be determined. The planned work, if successful, would provide a basis for engineering functional human cardiac grafts using cardiac and VEGF transfected cells derived from adult human stem cell sources. Our current inability to vascularize and perfuse thick cell masses has hindered efforts to build many types of tissues, including, most critically, cardiac muscle.